The adjustment of a limb during movement depends on exteroceptive and interoceptive guidance. This is achieved by interactions of sensorimotor systems at several levels of the neuraxis, conspicuously by the cerebellum and cerebrum. The specific aim of the proposed research is to study cerebellar control of indentifiable neural systems during voluntary movements. Firing patterns of single cells in motorsensory cortex and in nuclei receiving cerebral and cerebellar outflow will be correlated with voluntary motor performance of trained monkeys. Results obtained in control conditions will be compared with those during reversible cerebellar dysfunction produced by cooling of cerebellar nuclei.